1. Field of the Invention
The present invention relates to a drive of a variable valve lift mechanism for driving a control shaft controlling a variable valve lift mechanism provided between an engine valve and an engine valve operating cam in order to change the amount of lift of the engine valve.
2. Description of the Related Art
In Japanese Patent Application Laid-open No. 2002-364317, the present applicant already proposed a valve operating system of an internal combustion engine having a variable valve lift mechanism for continuously varying the amount of lift (valve opening degree) of an intake valve serving as an engine valve. This engine valve operating system is constituted so as to rotation-drive a sector-shaped worm wheel by a worm rotation-driven by, for example, a motor; pivot a lever directly connected to the worm wheel; and change the transmission rate of a cam lift to the intake valve. Driving mechanisms, such as a worm and a worm wheel, are directly built in a cylinder head or cylinder block.
However, using a configuration in which the main part of a driving mechanism is built in an engine body leads to disadvantages that not only the structure of the engine becomes complex but also the engine body need to be inevitably disassembled to a certain extent for maintenance of the driving mechanism.